The present invention relates generally to operations performed in subterranean wells and, in an embodiment described herein, more particularly provides apparatus and methods for completing and producing a subterranean well having multiple wellbores.
It is well known in the art of drilling subterranean wells to form a parent bore into the earth and then to form one or more bores extending laterally therefrom. Generally, the parent bore is first cased and cemented, and then a tool known as a whipstock is positioned in the parent bore casing. The whipstock is specially configured to deflect milling bits, drill bits, and/or other cutting tools in a desired direction for forming a lateral bore. A mill is typically lowered into the parent bore suspended from drill pipe and is radially outwardly deflected by the whipstock to mill a window in the parent bore casing and cement. Directional drilling techniques may then be employed to direct further drilling of the lateral bore outwardly from the window as desired.
The lateral bore may then be cased by inserting a tubular liner from the parent bore, through the window previously cut in the parent bore casing and cement, and into the lateral bore. In a typical lateral bore casing operation, the liner extends somewhat upwardly into the parent bore casing and through the window when the casing operation is finished. In this way, an overlap is achieved wherein the lateral bore liner is received in the parent bore casing above the window. In another type of lateral bore casing operation, the liner is completely received within the lateral bore and does not extend into the parent bore when the casing operation is finished.
The lateral bore liner is then cemented in place by forcing cement between the liner and the lateral bore. Where the liner extends into the parent bore, the cement is typically also forced between the liner and the window, and between the liner and the parent bore casing where they overlap. In this case, the cement provides a seal between the liner, the parent bore casing, the window, and the lateral bore. Where the liner does not extend into the parent bore, the cement provides a seal between the liner and the lateral bore.
Further operations may then be performed in completing and/or producing the well. For example, one or more tubing strings may be installed in the well to conduct fluids from formations intersected by the parent and lateral bores to the earth's surface, or to inject fluid into one or more of the formations. Unfortunately, these completion and/or production operations do not provide means whereby fluid flow through the tubing strings may be regulated in relatively close proximity to the formations and controlled from the earth's surface, in order to regulate rates of fluid flow from or into each of the formations, regulate the commingled proportions of fluids produced or injected into each of the formations, control rates of production or injection to comply with regulations affecting such matters, etc.
For example, a flow choke, inline orifice or other flow regulating device installed at the earth's surface is capable of influencing the rate of fluid flow through a single tubing string. However, when that tubing string conducts fluid produced from multiple formations or multiple intervals, the flow choke or inline orifice is not capable of regulating the proportional rate of fluid flow from each formation or interval. Of course, a separate flow choke or inline orifice may be provided for each formation or interval, but that would require a separate tubing string extending to the earth's surface for each formation or interval, which would be expensive and often impossible to achieve. Additionally, it is well known that wellbore storage effects make it much more desirable to regulate fluid flows in close proximity to the formations or intervals, rather than at the earth's surface.
As another example, flow regulating devices may be installed in the well, but past methods of accomplishing this have proved to be unsatisfactory. Most such flow regulating devices require intervention into the well to vary the rate of fluid flow therethrough, such as by shifting a sleeve using a shifting tool conveyed by wireline, slickline, tubing, etc. Others of such flow regulating devices obstruct the inner diameter of the tubing string in which they are installed.
From the foregoing, it can be seen that it would be quite desirable to provide a method of completing and/or producing a well which does not rely on flow regulating devices installed at the earth's surface, and which does not require intervention into the well to vary rates of fluid flow into or out of various formations or intervals, but which permits accurate and convenient regulation of fluid flow into or out of formations or intervals intersected by the well. It is accordingly an object of the present invention to provide such a method and associated apparatus.